Power transmission device for noncontact power supply device

ABSTRACT

A power transmission device for a noncontact power supply device includes a resonant circuit that outputs an alternating magnetic flux by power from a power source circuit, and switching elements for making the resonant circuit generate an alternating magnetic flux, and transmits power to a power receiving coil of a power reception device by the alternating magnetic flux. A power transmission controller of the power transmission device includes a transmission mode of supplying alternating power to the resonant circuit by repeating ON and OFF of switching elements by controlling switching elements. ON time in one cycle of operation of each of switching elements used in the transmission mode is a first fixed value. Accordingly, the power transmission device in a simplified configuration can be provided.

RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. § 371 ofInternational Patent Application No. PCT/JP2016/001678, filed on Mar.23, 2016, which in turn claims the benefit of Japanese Application No.2015-078054, filed on Apr. 6, 2015, the entire disclosures of whichApplications are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a power transmission device for anoncontact power supply device.

BACKGROUND ART

A conventional noncontact power supply device includes a resonantcircuit, and a plurality of switching elements. A power-transmissionresonant circuit outputs an alternating magnetic flux by power suppliedfrom a power source circuit. A plurality of switching elements perform aswitching operation so as to generate an alternating magnetic flux inthe resonant circuit.

The noncontact power supply device supplies alternating power to theresonant circuit by controlling the plurality of switching elements. Theresonant circuit outputs the alternating magnetic flux by being suppliedwith the alternating power. The output alternating magnetic flux istransmitted to a power reception device. As a result, power is suppliedto a load of the power reception device.

In this case, an input current supplied to the resonant circuit or anoutput current output from the resonant circuit may shift from adesigned current value. This occurs mainly due to a manufacturingvariation in a capacitor, a coil, or other part that configures eachresonant circuit. When the input current or the output current isshifted from the designed current value, power transmission efficiencyis likely to decrease.

Thus, there is disclosed a noncontact power supply device that includesa method of detecting a current input to a resonant circuit andchanging, based on a detection result, a frequency of a current suppliedto a plurality of switching elements (for example, refer to PTL 1).

However, according to the method of the noncontact power supply device,it is necessary to mount a circuit for feedback. Therefore, this methodis contradictory to simplification of the noncontact power supplydevice.

CITATION LIST Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 2014-207795

SUMMARY OF THE INVENTION

The present invention provides a power transmission device for anoncontact power supply device which contributes to simplification of aconfiguration.

Specifically, one exemplary embodiment of the present invention providesa power transmission device for a noncontact power supply device, thepower transmission device including a resonant circuit that outputs analternating magnetic flux by power supplied from a power source circuit;a plurality of switching elements that are switched such that analternating magnetic flux is generated in the resonant circuit; and apower transmission controller that controls the plurality of switchingelements to transmit power to a power receiving coil of a powerreception device by the alternating magnetic flux. The powertransmission controller includes a transmission mode for supplyingalternating power to the resonant circuit by repeating the on and off ofthe plurality of switching elements. Then, ON time in one cycle ofoperation of the switching elements in the transmission mode is set as afirst fixed value.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a noncontact power supply deviceaccording to an exemplary embodiment.

FIG. 2 is a front view of the noncontact power supply device from whicha head of an electric toothbrush in FIG. 1 is removed.

FIG. 3 is a front view of the electric toothbrush in FIG. 2.

FIG. 4 is a side view of the electric toothbrush in FIG. 2.

FIG. 5 is a rear view of the electric toothbrush in FIG. 2.

FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 3.

FIG. 7 is a side view of the electric toothbrush from which a grip partand a lower cap in FIG. 2 are removed.

FIG. 8 is a front view of the electric toothbrush from which the grippart, an upper cap, and the lower cap in FIG. 2 are removed.

FIG. 9 is a front view of a charging stand in FIG. 1.

FIG. 10 is a side view of the charging stand in FIG. 1.

FIG. 11 is a rear view of the charging stand in FIG. 1.

FIG. 12 is a plan view of the charging stand in FIG. 1.

FIG. 13 is a bottom view of the charging stand in FIG. 1.

FIG.14 is a cross-sectional view taken along line 14-14 in FIG. 9.

FIG.15 is a cross-sectional view taken along line 15-15 in FIG. 10.

FIG. 16 is a plan view of the charging stand from which a top surface ofa support part in FIG. 9 is removed.

FIG. 17 is a bottom view of the charging stand from which a bottom plateof a base in FIG. 9 is removed.

FIG. 18 is a cross-sectional view taken along line 18-18 in FIG. 2.

FIG. 19 is a cross-sectional view taken along line 19-19 in FIG. 2.

FIG. 20 is a schematic view showing a disposition relationship between apower transmitting coil and a power receiving unit in FIG. 18.

FIG. 21 is a block diagram of the power transmission device for thenoncontact power supply device in FIG. 1.

FIG. 22 is a block diagram of a magnetism collecting device and thepower reception device for the noncontact power supply device in FIG. 1.

FIG. 23 is a timing chart showing a first example of control of theswitching elements which is performed by the power transmissioncontroller in FIG. 21.

FIG. 24 is a graph showing a relationship between a current and a drivefrequency of the noncontact power supply device in FIG. 1.

FIG. 25 is a timing chart showing a second example of control of theswitching elements which is performed by the power transmissioncontroller in FIG. 21.

FIG. 26 is a timing chart showing a third example of control of theswitching elements which is performed by the power transmissioncontroller in FIG. 21.

FIG. 27 is a timing chart showing a fourth example of control of theswitching elements which is performed by the power transmissioncontroller in FIG. 21.

FIG. 28 is a timing chart showing a fifth example of control of theswitching elements which is performed by the power transmissioncontroller in FIG. 21.

FIG. 29 is a timing chart showing a sixth example of control of theswitching elements which is performed by the power transmissioncontroller in FIG. 21.

FIG. 30 is a graph showing a relationship between a coupling coefficientof a power transmitting coil and a magnetism collecting coil and anoutput current according to an example.

FIG. 31 is a cross-sectional view schematically showing a powerreceiving unit in FIG. 20.

FIG. 32 is a cross-sectional view schematically showing a powerreceiving unit of a comparative example.

FIG. 33 is a block diagram of a modification of the power transmissiondevice in FIG. 21.

FIG. 34 is a timing chart showing an example of control of the switchingelements which is performed by the power transmission controller of thepower transmission device according to the modification in FIG. 33.

DESCRIPTION OF EMBODIMENT

Hereinafter, an exemplary embodiment of the present invention will bedescribed with reference to the drawings. In the following description,the same reference numerals are attached to the same or correspondingparts, and redundant description will be omitted. The present inventionis not limited by the present exemplary embodiment.

Exemplary Embodiment

Hereinafter, a configuration of a noncontact power supply deviceaccording to the present exemplary embodiment will be described withreference to FIG. 1 to FIG. 20, mainly, FIG. 1 to FIG. 8.

As shown in FIG. 1, noncontact power supply device 1 of the presentexemplary embodiment includes a small electric device and charging stand80. In the following, for the small electric device, electric toothbrush10 which is an oral hygiene device will be described as an example.

Electric toothbrush 10 includes body 20 in a columnar shape, and head 11detachably attached to output shaft 31 (refer to FIG. 2) of drive unit30 (refer to FIG. 6) of body 20.

Body 20 includes case 21, display unit 24, and power source button 25shown in FIG. 2, support body 29, drive unit 30, power source unit 40,and substrate 50 shown in FIG. 7, and power reception device 60 andmagnetism collecting device 70 shown in FIG. 6. Drive unit 30, powersource unit 40, substrate 50, power reception device 60, and magnetismcollecting device 70 are supported by support body 29, and areaccommodated inside case 21.

Case 21, as shown in FIG. 3, has grip part 22 in a hollow structure,upper cap 26 that closes an upper part of grip part 22, and lower cap 27that closes a lower part of grip part 22.

Grip part 22 includes a tapered shape in which an outer diameter becomessmaller from upper cap 26 toward lower cap 27. Specifically, grip part22, includes a cross section along a width direction, in a substantiallyelliptical shape (including an elliptical shape), as shown in FIG. 19.

As shown in FIG. 4 and FIG. 5, grip part 22 includes protrusion 23Aprotruding outward from grip part 22, on the rear surface. Protrusion23A is extended in a peripheral direction of grip part 22. Further,protrusion 23A is discontinuously formed in a peripheral direction ofgrip part 22.

Further, grip part 22 includes supported part 23 at a lower portion thanprotrusion 23A, with protrusion 23A as an upper end. Supported part 23is covered with support part 84 of charging stand 80, when grip part 22is supported by charging stand 80 (refer to FIG. 2).

Upper cap 26 of case 21 includes front cap 26A and inner cap 26Bsuperposed on an inner side of front cap 26A, as shown in FIG. 6. Uppercap 26 is fitted to an upper part of grip part 22.

Inner cap 26B, as shown in FIG. 7, includes coupling part 26C in acircular cylindrical shape protruding downward. Hole 26D is formed incoupling part 26C.

Upper cap 26 is attached with disk-shaped elastic member 28A on an uppersurface, as shown in FIG. 8. Output shaft 31 of drive unit 30 describedlater is provided so as to protrude from elastic member 28A. As shown inFIG. 6 and FIG. 7, between upper cap 26 and an inner periphery of grippart 22, elastic member 28B formed of an O-ring, for example, isattached.

Upper cap 26 is attached to support body 29, by being fitted to hook 29Ain which hole 26D of coupling part 26C is formed on an outer peripheryof support body 29.

Lower cap 27 has a double structure of front cap 27C and inner cap 27B,as shown in FIG. 6. Lower cap 27 is fitted to a lower part of grip part22. Then, lower cap 27 is attached to support body 29 by screwing screwB from below. Between lower cap 27 and the inner periphery of grip part22, elastic member 28C formed of an O-ring, for example, is attached.Similarly, between lower cap 27 and a bottom surface of support body 29,elastic member 28D formed of an O-ring, for example, is attached.

Elastic members 28A to 28D prevent water from entering the inside ofcase 21 and vibration inside body 20 from being transmitted to case 21.Further, the double structure of upper cap 26 and lower cap 27 preventswater from entering the inside of case 21 and vibration generated insidebody 20 from being transmitted to case 21.

Support body 29 attached with upper cap 26, drive unit 30, power sourceunit 40, substrate 50, and power reception device 60 is inserted into anopening at an upper part of grip part 22. Then, lower cap 27 is attachedand is screwed with screw B from below grip part 22. As a result, body20 of electric toothbrush 10 is assembled.

Further, as shown in FIG. 3, display unit 24 is provided in body 20 toenable a user to visually recognize display unit 24. Display unit 24includes ion display unit 24A, drive-mode display unit 24B,residual-quantity display unit 24C, and charge display unit 24D. Iondisplay unit 24A displays by lighting that head 11 is generating ion.Drive-mode display unit 24B displays while changing a lighting state,for example, according to a kind (a mode) of vibration of head 11. Akind of vibration of head 11 is controlled by a drive mode of drive unit30 (refer to FIG. 6). Residual-quantity display unit 24C displays aresidual capacity and the like, according to a voltage of rechargeablebattery 41 (refer to FIG. 6) of power source unit 40.

Display unit 24 is configured, for example, with an LED (Light EmittingDiode) that is mounted on substrate 50, as shown in FIG. 8.

In this case, grip part 22 is formed of a material of high lighttransmittance at a portion opposite to display unit 24 to enable theuser to visually recognize a lighting state of display unit 24. In thiscase, a hole may be formed in grip part 22 such that at least a part ofdisplay unit 24 is exposed from a surface of grip part 22.

Further, display unit 24 is disposed at a different position fromsupported part 23 of body 20, for example, at an opposite side.Therefore, as shown in FIG. 2, even when body 20 is supported bycharging stand 80, the user can visually recognize the lighting state ofdisplay unit 24. Particularly, by visually recognizing charge displayunit 24D, the user can easily grasp whether electric toothbrush 10 isbeing charged.

Power source button 25 is attached to body 20 such that the user canoperate power source button 25. Power source button 25 is provided inbody 20 such that at least a part of power source button protrudesthrough the surface of grip part 22. When the user presses power sourcebutton 25, a drive controller (not shown) starts driving head 11, basedon a drive mode set in drive unit 30 (refer to FIG. 6).

Output shaft 31 of drive unit 30 is supported by body 20 in a state ofprotruding through elastic member 28A at an upper part of case 21, asshown in FIG. 6. Drive unit 30 is exemplified by an electric linearactuator, for example. When drive unit 30 is driven, output shaft 31vibrates. Therefore, head 11 (refer to FIG. 1) attached to output shaft31 vibrates. Accordingly, a predetermined operation (tooth brushing, forexample) is performed on the user. Drive unit 30 may be configured as anelectric motor, and output shaft 31 may be configured as an eccentricshaft which is eccentric to a rotation axis of the electric motor. Inthis case, along with drive of the electric motor, the eccentric shaftas output shaft 31 vibrates. Accordingly, head 11 can be vibrated.

Power source unit 40 includes rechargeable battery 41 as a load of thenoncontact power supply device. For rechargeable battery 41, a secondarybattery such as a lithium ion battery is exemplified, for example. Anupper end and a lower end of rechargeable battery 41 are supported bymetal plate 42 provided in support body 29. Power source unit 40supplies power to drive unit 30.

Substrate 50 is disposed inside grip part 22 along inner periphery ofgrip part 22.

Power receiving unit 61 of power reception device 60 is disposed nearbottom surface 27A inside grip part 22. Power receiving unit 61 includespower receiving coil 62 and magnetism collecting coil 71 of a magnetismcollecting circuit that configures a magnetism-collecting resonantcircuit of magnetism collecting device 70, as shown in FIG. 6. Powerreceiving coil 62 and magnetism collecting coil 71 are formed by beingwound around bobbin-shaped magnetic core 63, for example. Powerreceiving coil 62 is wound around an outer periphery of magnetismcollecting coil 71. Magnetic core 63 is attached to a base portion (apower-reception core holding portion) made of resin, with a core adheredto the base portion. Between magnetism collecting coil 71 and powerreceiving coil 62, an insulation tape not shown is wound for insulation.Power receiving coil 62 and an element configuring a circuit ofsubstrate 50 are electrically connected to each other with lead frame 51shown in FIG. 7. Lead frame 51 is provided at a lower end part ofsubstrate 50, and supports substrate 50.

Above drive unit 30 is disposed near upper cap 26 inside grip part 22,as shown in FIG. 6. Similarly, power receiving coil 62 is disposed nearlower cap 27. Further, power source unit 40 is disposed between driveunit 30 and power receiving coil 62.

As described above, electric toothbrush 10 as an example of a smallelectric device of noncontact power supply device 1 according to thepresent exemplary embodiment is configured.

Hereinafter, a configuration of charging stand 80 of noncontact powersupply device 1 according to the present exemplary embodiment will bedescribed with reference to FIG. 9 to FIG. 20.

Charging stand 80 has case 81, connection part 90, substrate 100, andpower transmission device 110, as shown in FIG. 14, for example.Connection part 90 is connected with power source line 120 forconnection to alternating-current power source AC (refer to FIG. 21).Substrate 100 and power transmission device 110 are accommodated insidecase 81.

Case 81 has base 82, pillar 83, and support part 84. Base 82 is forsetting case 81 on a setting surface of furniture or the like. Pillar 83is provided so as to extend upward from a part of an outer peripheralpart of base 82. Support part 84 is provided to protrude in a lateraldirection (a horizontal direction) from an upper end of pillar 83.Support part 84 and base 82 are provided so as to extend in the samedirection relative to pillar 83, as shown in FIG. 10. That is, supportpart 84 and base 82 are oppositely disposed.

Base 82 is formed in a substantially circular shape (including acircular shape) in a plan view, viewed from above, shown in FIG. 12.

Base 82 includes top plate 82A and bottom plate 82C as shown in FIG. 11.Top surface 82B configured of top plate 82A of base 82 has a flat shape,for example. Therefore, the user can easily wipe out stain from topsurface 82B. Top plate 82A may be configured to be detachable from base82. In this case, the user can take out top plate 82A and easily washtop plate 82A with water. Further, as shown in FIG. 13, bottom surface82D configured of bottom plate 82C of base 82 has a flat shape, forexample. Therefore, base 82 can be stably kept stood, against fall invarious directions, in a state that charging stand 80 itself or electrictoothbrush 10 is mounted.

Support part 84 has hole 84A formed to extend in a height direction (adirection orthogonal to a paper surface), as shown in FIG. 12. That is,support part 84 has hole 84A in an approximately ring shape (including aring shape) into which body 20 (refer to FIG. 1) of electric toothbrush10 can be inserted. Hole 84A is formed in an elliptical shape in a planview, viewed from above, shown in FIG. 12. In this case, as shown inFIG. 14, the top surface of support part 84 and the inner peripheralsurface of hole 84A are integrally formed. Therefore, as compared with acase of forming the top surface of support part 84 and the innerperipheral surface of hole 84A by combining separate members, supportpart 84 can be structured such that a liquid such as water cannot easilyenter the inside of support part 84.

Further, the elliptical shape of hole 84A is formed in a shape similarto a shape of the elliptical shape of grip part 22, as shown in FIG. 19.An inner diameter of hole 84A is formed slightly larger than an outerdiameter of supported part 23 out of grip part 22 of body 20. Therefore,supported part 23 of grip part 22 can be easily inserted into hole 84A.Hole 84A and supported part 23 have cross sections in elliptical shapesas described above. Therefore, when supported part 23 is inserted intohole 84A, rotation of body 20 is prevented.

Further, an opening on an upper side of hole 84A is formed in a curvedsurface shape such that an inner diameter of hole 84A expands toward anupper direction, as shown in FIG. 14. Therefore, in the case ofinserting body 20 (refer to FIG. 18) into hole 84A from above, bottomsurface 27A of body 20 is easily guided to an inner side (downward)along the opening of hole 84A.

Further, hole 84A includes two recesses 84B on an edge of an upper sideopening, as shown in FIG. 12. An upper surface of recess 84B has aplanar shape in the direction orthogonal to the height direction.Therefore, when body 20 is inserted into hole 84A, protrusion 23A ofbody 20 is caught in recess 84B of hole 84A, as shown in FIG. 18, and nomore insertion is stopped. In the above state, distance LA from recess84B to top surface 82B of base 82 is larger than distance LB fromprotrusion 23A to bottom surface 27A which is formed of lower cap 27 ofbody 20. That is, when body 20 is inserted into hole 84A, gap S (LA-LB)is formed between bottom surface 27A of body 20 and top surface 82B ofbase 82. As a result, body 20 of electric toothbrush 10 is supported oncharging stand 80 in a state that bottom surface 27A is floated from topsurface 82B of base 82. Gap S is preferably about 1 mm to 30 mm, andmore preferably, about 16 mm, for example.

Further, two recesses 84B, for example, are formed in the opening ofhole 84A. As described above, hole 84A is formed in an elliptical shape.Therefore, body 20 can be inserted into hole 84A at a position of 180degrees different in a peripheral direction with respect to chargingstand 80. Accordingly, the user can optionally select, at time ofinserting body 20, to which one of the two recesses 84B, protrusion 23Aof body 20 should be hooked.

Hole 84A of support part 84 includes two guide parts 84C protrudingtoward a center axis of hole 84A, on an inner periphery, as shown inFIG. 14. Two guide parts 84C are provided at opposite (facing) positionswith the center axis of hole 84A interposed therebetween. Further, twoguide parts 84C are formed at mutually different positions in an axialdirection (a height direction) of hole 84A. Therefore, body 20 ofelectric toothbrush 10 is inserted into hole 84A while two guide parts84C maintain a posture of body 20 such that a height direction of body20 is parallel to an axial direction of hole 84A.

Connection part 90 of charging stand 80 is provided on an opposite sideof base 82, on a lower side of pillar 83, as shown in FIG. 15.Connection part 90 is formed in a recess shape inward from an outerperipheral side surface of pillar 83, for example. Connection part 90includes, inside, terminal 93 connected to a terminal (not shown) ofpower source line 120. Via terminal 93, power is supplied from powersource line 120, and supplied power is supplied to power transmissiondevice 110.

Connection part 90 has a stepped structure as a waterproof structure.Specifically, the stepped structure of connection part 90 includes largediameter part 91 on a surface side of case 81, and small diameter part92 on a back side of large diameter part 91. On the other hand, powersource line 120 includes small diameter part 122 on a front end side tobe inserted into connection part 90, and large diameter part 123 whichis continuous with small diameter part 122. Therefore, when power sourceline 120 is connected to connection part 90, small diameter part 122 ofpower source line 120 is inserted into small diameter part 92 ofconnection part 90. Similarly, large diameter part 123 of power sourceline 120 is inserted into large diameter part 91 of connection part 90.In this case, connection part 90 is formed such that a gap between largediameter part 123 and large diameter part 91 (for example, 0 mm to 0.4mm) is smaller than a gap between small diameter part 122 and smalldiameter part 92 (for example, 1 mm or more). Therefore, water enteringfrom an outside to the inside of connection part 90 remains in largediameter part 91 of connection part 90 more easily than in smalldiameter part 122 of power source line 120, by a capillary phenomenon.Accordingly, adhesion of water entering connection part 90 to terminal93 can be prevented. As a result, reliability in connection part 90 canbe maintained for a long time.

Substrate 100 of charging stand 80 is provided inside base 82, as shownin FIG. 14.

Power transmitting coil 111 is provided inside support part 84, as shownin FIG. 16. Power transmitting coil 111 configures a primary-powersupply part of power transmission device 110. An element configuring thecircuit of substrate 100 and power transmitting coil 111 areelectrically connected by lead wire 101 disposed through an inside ofpillar 83, as shown in FIG. 17.

Next, a disposition relationship between power transmitting coil 111 andpower receiving unit 61 disposed in charging stand 80 will be describedwith reference to FIG. 20.

As shown in FIG. 20, in a state that body 20 is supported by chargingstand 80, center TCC of power transmitting coil 111 in an axialdirection and center RCC of magnetism collecting coil 71 of powerreceiving unit 61 in an axial direction are disposed in a shiftedmanner. Specifically, in the axial direction, center RCC of magnetismcollecting coil 71 is positioned below center TCC of power transmittingcoil 111. Further, upper end RCT of magnetism collecting coil 71 ispositioned above lower end TCL of power transmitting coil 111.Accordingly, in the axial direction, at least a part of magnetismcollecting coil 71 and at least a part of power transmitting coil 111are disposed in an overlapping manner. In this case, distance LC betweencenter TCC of power transmitting coil 111 and center RCC of magnetismcollecting coil 71 of power receiving unit 61 is preferably less than ahalf of length LD of power transmitting coil 111 in the axial direction.This is because when distance LC exceeds a half of length LD, couplingof the power transmitting coil and the magnetism collecting coil becomestoo small.

As described above, charging stand 80 of noncontact power supply device1 of the present exemplary embodiment is configured.

Hereinafter, a circuit configuration of power transmission device 110for noncontact power supply device 1 according to the present exemplaryembodiment will be described in detail with reference to FIG. 21.

Power transmission device 110 of charging stand 80 is connected toalternating-current power source AC through power source line 120 andconnection part 90, as shown in FIG. 21. Power source line 120 includespower source circuit 121 for converting alternating-current power ofalternating-current power source AC into direct-current power.

Power transmission device 110 includes power transmitting coil 111, andfirst switching element 112A, second switching element 112B, capacitors113A, 113B, first drive circuit 114A, second drive circuit 114B, powertransmission controller 115, power-transmission resonant capacitor 116,current detecting circuit 117, and voltage detecting circuit 118 thatare mounted on substrate 100.

First switching element 112A and second switching element 112B convertdirect current (power) obtained by conversion in power source circuit121, into alternating power by switching operation of ON/OFF. Thealternating power obtained by conversion is supplied to powertransmitting coil 111. In this case, power source circuit 121 functionsas a constant-voltage power source of 5 V, for example.

First switching element 112A and second switching element 112B areconnected in series. First switching element 112A and second switchingelement 112B are configured of field-effect transistors (FET), forexample. Specifically, first switching element 112A is configured of aP-channel FET, and second switching element 112B is configured of anN-channel FET. Then, a half-bridge circuit is configured of firstswitching element 112A and second switching element 112B. Further, firstswitching element 112A is connected to capacitor 113A, and secondswitching element 112B is connected to capacitor 113B. Capacitors 113Aand 113B have the same capacitances, and divide a direct-current voltageapplied to the half-bridge circuit into about a half (½).

First switching element 112A is connected to first drive circuit 114A.Second switching element 112B is connected to second drive circuit 114B.

Power transmission controller 115 controls power supplied from firstdrive circuit 114A to first switching element 112A, and from seconddrive circuit 114B to second switching element 112B. Power transmissioncontroller 115 outputs a command signal of PWM (Pulse Width Modulation)to first drive circuit 114A and second drive circuit 114B, for example.First drive circuit 114A and second drive circuit 114B supply powerbased on an input PWM signal to first switching element 112A and secondswitching element 112B. Each of first switching element 112A and secondswitching element 112B generates alternating power to be supplied topower-transmission resonant capacitor 116, by repeating a switchingoperation of ON/OFF.

Power-transmission resonant capacitor 116 is disposed to be connected inseries between a connecting point of first switching element 112A andsecond switching element 112B, and power transmitting coil 111.Power-transmission resonant capacitor 116 and power transmitting coil111 configure a power-transmission resonant circuit. In this case, apower-transmission resonance frequency of power-transmission resonantcapacitor 116 and power transmitting coil 111 configuring apower-transmission resonant circuit is set to become smaller than thedrive frequency for driving first switching element 112A and secondswitching element 112B.

Current detecting circuit 117 includes resistor 117A and amplifyingcircuit 117B. Resistor 117A is connected to a ground side of powertransmission device 110, and is used for detecting an input currentinput to power transmission device 110. Amplifying circuit 117Bamplifies a voltage generated on both ends of resistor 117A. Amplifyingcircuit 117B converts a magnitude of a current detected by resistor 117Ainto a voltage, amplifies the voltage, and outputs the voltage to powertransmission controller 115.

Voltage detecting circuit 118 is connected to a connecting point betweenpower-transmission resonant capacitor 116 and power transmitting coil111, and is connected to a ground side via two resistors 118A, 118B.Voltage detecting circuit 118 detects a resonance voltage V as a voltageof the power-transmission resonant circuit. Voltage detecting circuit118 outputs resonance voltage V detected at a connecting point betweentwo resistors 118A, 118B, to power transmission controller 115. Powertransmission controller 115 controls a transmission mode and a standbymode described later, by switching between the modes, based on resonancevoltage V. That is, when resonance voltage V is lower than apredetermined voltage, power transmission controller 115 determines thatbody 20 shown in FIG. 18 is supported on charging stand 80 and sets themode to the transmission mode. On the other hand, when resonance voltageV is at or higher than the predetermined voltage, power transmissioncontroller 115 determines that body 20 is not supported on chargingstand 80 and sets the mode to the standby mode. In the standby mode,less power than that in the transmission mode is supplied to powertransmitting coil 111 of power transmission device 110.

As described above, the circuit of power transmission device 110 fornoncontact power supply device 1 is configured.

Hereinafter, a circuit configuration of magnetism collecting device 70and power reception device 60 for noncontact power supply device 1 willbe described with reference to FIG. 22.

Magnetism collecting device 70 of electric toothbrush 10 includesmagnetism collecting coil 71 and magnetism-collecting resonant capacitor72, as shown in FIG. 22. Magnetism collecting coil 71 andmagnetism-collecting resonant capacitor 72 form a magnetism collectingcircuit that configures the magnetism-collecting resonant circuit.Further, magnetism-collecting resonant capacitor 72 is mounted onsubstrate 50 (refer to FIG. 6).

Power reception device 60 of electric toothbrush 10 includes powerreceiving coil 62 that is magnetically coupled with magnetism collectingcoil 71, diode 64 and smoothing capacitor 65 that configure a rectifiercircuit, current detecting circuit 66, power reception controller 67,switch 68, timing detecting circuit 69, and charge display unit 24D.Diode 64, smoothing capacitor 65, current detecting circuit 66, powerreception controller 67, switch 68, and timing detecting circuit 69 aremounted on substrate 50, and are connected to rechargeable battery 41which is a load. Accordingly, magnetism collecting device 70 and powerreception device 60 are not electrically connected, and are magneticallycoupled. Therefore, magnetism collecting device 70 is not connected torechargeable battery 41 which is a load.

Next, operation and advantageous effects of power reception device 60and magnetism collecting device 70 will be described.

First, in the transmission mode, the alternating magnetic flux generatedfrom power transmitting coil 111 shown in FIG. 21 interlinks withmagnetism collecting coil 71 shown in FIG. 20. Then, by magneticresonance of power transmission device 110 and magnetism collectingdevice 70, power is transmitted from power transmitting coil 111 tomagnetism collecting coil 71. Power transmitted to magnetism collectingcoil 71 is transmitted from magnetism collecting coil 71 to powerreceiving coil 62, based on electromagnetic induction by power receptiondevice 60 and magnetism collecting device 70. Accordingly, alternatingpower is generated in power receiving coil 62. That is, powertransmitting coil 111 of power transmission device 110 (refer to FIG. 6)transmits power to power receiving coil 62 of power reception device 60,via magnetism collecting coil 71 of magnetism collecting device 70. Thatis, power receiving unit 61 including power transmitting coil 111, powerreceiving coil 62, and magnetism collecting coil 71 configures anoncontact power transmitting unit. The alternating power generated inpower receiving coil 62 of power receiving unit 61 is converted from analternating current to a direct current by diode 64. Diode 64 isconnected to smoothing capacitor 65, and rechargeable battery 41 whichis a load. Smoothing capacitor 65 reduces noise contained in the directcurrent obtained by conversion by diode 64. Rechargeable battery 41 issupplied with the direct current obtained by conversion by diode 64.Between diode 64 and rechargeable battery 41, there is disposed switch68 for turning ON/OFF the supply of the converted direct current.

Current detecting circuit 66 of power reception device 60 includesresistor 66A and amplifying circuit 66B. Resistor 66A is connected to aground side of power reception device 60, and is used for detecting aninput current input to rechargeable battery 41 which is a load.Amplifying circuit 66B amplifies a voltage generated on both ends ofresistor 66A. Amplifying circuit 66B converts a magnitude of a currentdetected by resistor 66A into a voltage, amplifies the voltage, andoutputs the voltage to power reception controller 67.

Power reception controller 67 controls a charge operation ofrechargeable battery 41, by switching the ON/OFF of switch 68, based ona voltage detected by current detecting circuit 66. That is, powerreception controller 67 switches the operation between supply andnon-supply of power to rechargeable battery 41. Specifically, when thevoltage of rechargeable battery 41 is less than a predetermined voltage(3 V, in the case of a lithium ion battery, for example), powerreception controller 67 switches switch 68 to ON, and starts charging.On the other hand, when the voltage of rechargeable battery 41 is equalto or greater than a predetermined voltage (4.2 V, in the case of alithium ion battery, for example), power reception controller 67switches switch 68 to OFF, and stops charging.

Power reception controller 67 switches the display of charge displayunit 24D. Specifically, power reception controller 67 turns on chargedisplay unit 24D when charge to rechargeable battery 41 is beingperformed. On the other hand, when charge to rechargeable battery 41 isnot being performed, charge display unit 24D is not turned on.Accordingly, this can make the user recognize whether charging is beingperformed.

Furthermore, by switching between ON and OFF of switch 68, powerreception controller 67 communicates with power transmission controller115 of power transmission device 110 (refer to FIG. 21), and detectsbody 20. Power transmission controller 115 detects with voltagedetecting circuit 118 (refer to FIG. 21), resonance voltage V whichvaries by switching switch 68 of power reception device 60. Accordingly,power transmission controller 115 adjusts the output of the alternatingpower generated by power transmitting coil 111.

Timing detecting circuit 69 of power reception device 60 shown in FIG.22 detects presence or absence of a waveform, in a predetermined period,of alternating power generated by power receiving coil 62. The waveformdetected by timing detecting circuit 69 correlates with the output ofalternating power supplied to power transmitting coil 111 of powertransmission device 110 (refer to FIG. 21). Therefore, timing detectingcircuit 69 can detect presence or absence of alternating power suppliedto power transmitting coil 111. Timing detecting circuit 69 isconfigured of a transistor, for example.

Hereinafter, a detailed operation of timing detecting circuit 69 will bedescribed.

First, when alternating power is generated in power receiving coil 62, avoltage is continuously applied to power receiving coil 62. Therefore, atransistor configuring timing detecting circuit 69 continues in a stateof ON. In this case, timing detecting circuit 69 outputs first timingsignal SA to power reception controller 67. On the other hand, whenalternating power is not generated in power receiving coil 62, thetransistor becomes in a state of OFF. In this case, timing detectingcircuit 69 outputs second timing signal SB to power reception controller67. That is, power reception controller 67, based on first timing signalSA or second timing signal SB that is input, detects presence or absenceof alternating power supplied from power transmission device 110. Powerreception controller 67 performs control of ON/OFF operation of switch68 and control of a lighting operation of charge display unit 24D.

Next, switch control of the ON/OFF operation of first switching element112A and second switching element 112B, the switch control beingperformed by power transmission controller 115 of power transmissiondevice 110 will be described with reference to FIG. 21 and FIG. 23.

Power transmission controller 115 outputs from first drive circuit 114A,a PWM signal for causing gate G of first switching element 112A torepeat the ON/OFF operation, as shown in (a) in FIG. 23. The PWM signalincludes information of first ON time TXA corresponding to ON time TX inthe operation of one cycle T (for example, 7 μs) as a length for keepingfirst switching element 112A ON. In this case, as described above, firstswitching element 112A is configured of a P-channel FET. Therefore,first switching element 112A becomes in an ON state, when gate voltageVX of a low level (for example, 0 V) is applied to gate G. On the otherhand, first switching element 112A becomes in an OFF state, when gatevoltage VX of a high level (for example, 5 V as an input voltage frompower source circuit 121) is applied to gate G.

Further, power transmission controller 115 outputs from second drivecircuit 114B, a PWM signal for causing gate G of second switchingelement 112B to repeat the ON/OFF operation, as shown in (b) in FIG. 23.The PWM signal includes information of second ON time TXB correspondingto ON time TX in the operation of one cycle T (for example, 7 μs) as alength for keeping second switching element 112B ON. In this case, asdescribed above, second switching element 112B is configured of anN-channel FET. Therefore, second switching element 112B becomes in anOFF state, when gate voltage VY of a low level is applied to gate G. Onthe other hand, second switching element 112B becomes in an ON state,when gate voltage VY of a high level is applied to gate G.

Power transmission controller 115 outputs a PWM signal to gates G offirst switching element 112A and second switching element 112B such thatfirst ON time TXA in which first switching element 112A becomes ON andsecond ON time TXB in which second switching element 112B becomes ON arealternate in time sequence. Accordingly, as shown in (c) in FIG. 23, apower-transmitting coil current flowing through power transmitting coil111 of power transmission device 110 becomes in a sinusoidal waveform,for example.

In this case, as described above, a relationship betweenpower-transmission resonance frequency f1, drive frequency fD, andpower-reception resonance frequency f2 is set to satisfy f1<fD<f2.Power-transmission resonance frequency f1 is a resonance frequency of apower-transmission resonant circuit. Drive frequency fD is the frequencyof the PWM signal applied to gates G of first switching element 112A andsecond switching element 112B. Power-reception resonance frequency f2 isa resonance frequency of a magnetism collecting circuit itself or powerreception device 60 including a magnetism collecting circuit.

The relationship of f1<fD<f2 is realized by the following set ofconditions.

First, a value of each configuration element is set in a state that body20 is supported by charging stand 80 as shown in FIG. 1, and powerreceiving unit 61 and power transmitting coil 111 are disposed as shownin FIG. 18.

Specifically, the design value of inductance L of power transmittingcoil 111 is set to 4 μH. A design value of capacitance C ofpower-transmission resonant capacitor 116 is set to 0.36 μF. A designvalue of inductance L of magnetism collecting coil 71 is set to 14 μH. Adesign value of capacitance C of magnetism-collecting resonant capacitor72 is set to 77200 pF. A design value of inductance L of power receivingcoil 62 is set to 2 μH.

In this case, power-transmission resonance frequency f1 andpower-reception resonance frequency f2 are calculated in accordance withEquation (1).

f=1/(2π√LC)   (1)

That is, when each resonant circuit is designed in the above designvalue, power-transmission resonance frequency f1 becomes about 133 kHz,and power-reception resonance frequency f2 becomes about 153 kHz.

Then, drive frequency fD is set to 143 kHz, for example, so as tosatisfy the relationship of f1<fD<f2, based on designedpower-transmission resonance frequency f1 and power-reception resonancefrequency f2.

However, as described above, drive frequency fD may vary from the designvalue due to an influence of an oscillator which is a component. Forexample, in the case of setting drive frequency fD to 143 kHz, when avariation of ±0.5% from the design value occurs, drive frequency fDvaries in a range of about 142 kHz to 144 kHz.

Further, when power transmitting coil 111 and magnetism collecting coil71 vary by ±5% from a design value and power-transmission resonantcapacitor 116 and magnetism-collecting resonant capacitor 72 vary by ±5%from a design value, power-transmission resonance frequency f1 andpower-reception resonance frequency f2 become as follows. That is, dueto the variation in the components, power-transmission resonancefrequency f1 can be in a range of 126 kHz to 140 kHz, andpower-reception resonance frequency f2 can be in a range of 145 kHz to162 kHz.

Therefore, in noncontact power supply device 1 according to the presentexemplary embodiment, the design values of the components are set suchthat the relationship of f1<fD <f2 is maintained even when a variationin a general magnitude (for example, about ±5%) occurs in thecomponents, for example.

On the other hand, in a state that main body 20 is not supported bycharging stand 80, inductance L of power transmitting coil 111 becomesas follows.

In this case, magnetic core 63 configuring power receiving unit 61 isnot present near power transmitting coil 111. Therefore, inductance L ofpower transmitting coil 111 becomes smaller than that when powerreceiving unit 61 shown in FIG. 18 is positioned near power transmittingcoil 111.

That is, a value of inductance L of power transmitting coil 111 changesbetween a case of disposition when magnetic core 63 is present nearpower transmitting coil 111 shown in FIG. 18 and a case of dispositionwhen magnetic core 63 is not present. Therefore, in the presentexemplary embodiment, regardless of presence or absence of magnetic core63, an arrangement position and magnetic core 63 are designed such thatpower-transmission resonance frequency f3 is set to a frequency that isequal to or less than drive frequency fD. Power-transmission resonancefrequency f3 is a value corresponding to power-transmission resonancefrequency f1 of the power-transmission resonant circuit when magneticcore 63 is not present.

Specifically, the arrangement position and magnetic core 63 are designedsuch that a change in inductance L when magnetic core 63 is not nearpower transmitting coil 111 falls within −3%, for example. In this case,inductance L of power transmitting coil 111 in a state in which body 20is not supported by charging stand 80 is in a range of 3.7 μH to 4.1 μH.Accordingly, power-transmission resonance frequency f3 varies within arange of 128.3 kHz to 141.8 kHz from Equation (1). In this case, therelationship of f3<fD is also satisfied.

That is, power-transmission resonance frequency f1 when the couplingcoefficient of power transmitting coil 111 and magnetism collecting coil71 is included in a first range, and power-transmission resonancefrequency f3 when the coupling coefficient of power transmitting coil111 and magnetism collecting coil 71 is included in a second rangesmaller than the first range and when body is not disposed in powertransmission device, can be set to a frequency smaller than drivefrequency fD. The first range is a coupling coefficient of powertransmitting coil 111 and magnetism collecting coil 71 in a state thatbody 20 shown in FIG. 1 is supported by charging stand 80 and powerreceiving unit 61 and power transmitting coil 111 shown in FIG. 18 aredisposed. On the other hand, the second range is a coupling coefficientof power transmitting coil 111 and magnetism collecting coil 71 whenbody 20 is disposed apart from charging stand 80.

Further, in the present exemplary embodiment, the design value of eachcomponent is set such that power-transmission resonance frequency f1(f3) and power-reception resonance frequency f2 become values near drivefrequency fD. Specifically, power-transmission resonance frequency f1based on the design value is set to a frequency that is smaller (less)than drive frequency fD and equal to or higher than 85% of drivefrequency fD. Similarly, power-reception resonance frequency f2 based onthe design value is set to a frequency that is larger than (exceeds)drive frequency fD and equal to or less than 115% of drive frequency fD.When the value of power-reception resonance frequency f2 exceeds 85% andis less than 115%, required output and efficiency are not satisfied.Therefore, it is preferable that power-reception resonance frequency f2is set to fall within the above range.

Further, impedance Z of the resonant circuit of power transmissiondevice 110 is obtained by Equation (2) below. The value of r1 representsa resistance value of power transmitting coil 111.

Z=wL−1/wC+r1  (2)

Usually, as shown in (b), (c), (d) of FIG. 24, when power-transmissionresonance frequency f1 is closer to drive frequency fD, the inputcurrent of power transmission device 110, power-transmitting coilcurrent flowing through power transmitting coil 111, and the outputcurrent of power transmission device 110 increase.

On the other hand, in the case where power-transmission resonancefrequency f1 and power-reception resonance frequency f2 are close todrive frequency fD, when values of power transmitting coil 111,magnetism collecting coil 71, power-transmission resonant capacitor 116,and magnetism-collecting resonant capacitor 72 vary from the designvalues, impedance Z also varies from Equation (2). For example, as shownin (a) in FIG. 24, when power-transmission resonance frequency f1 isfirst power-transmission resonance frequency fx smaller than drivefrequency fD, impedance Z shows first impedance ZA higher than whenpower-transmission resonance frequency f1 coincides with drive frequencyfD. Further, when power-transmission resonance frequency f1 is smallerthan first power-transmission resonance frequency fx and is secondpower-transmission resonance frequency fy farther from drive frequencyfD, impedance Z shows second impedance ZB much higher than whenpower-transmission resonance frequency f1 coincides with drive frequencyfD.

That is, when impedance Z varies, the power-transmitting coil currentflowing through power transmitting coil 111 varies. Therefore, the inputcurrent and the output current also vary.

Accordingly, in the present exemplary embodiment, power transmissioncontroller 115 of power transmission device 110 prevents variation inthe power-transmitting coil current by the following method.

First, in response to power transmission device 110, power receptiondevice 60, and magnetism collecting device 70, power transmissioncontroller 115 measures in advance ON times TX, TY of a PWM signalapplied to gates G of first switching element 112A and second switchingelement 112B. Then, measured ON times TX, TY are stored in a storageunit of power transmission controller 115. Specifically, in the abovetransmission mode, power transmission controller 115 sets ON time TX offirst switching element 112A and second switching element 112B to firstON time TXA and second ON time TXB as first fixed values. On the otherhand, in the above standby mode, power transmission controller 115 setsON time TY of first switching element 112A and second switching element112B to first ON time TYA and second ON time TYB as second fixed values.Then, in the transmission mode and the standby mode, power transmissioncontroller 115 controls drive of first switching element 112A and secondswitching element 112B, based on the stored first fixed value and secondfixed value. Accordingly, the variation in the power-transmitting coilcurrent generated in power transmitting coil 111 of power transmissiondevice 110 is prevented.

Hereinafter, a method of setting first ON times TXA, TYA and second ONtimes TXB, TYB of first switching element 112A and second switchingelement 112B will be described with reference to FIG. 21. ON time TXcorresponds to the ON time in the above transmission mode. On the otherhand, ON time TY corresponds to the ON time in the above standby mode.

First, a method of setting ON time TX in the transmission mode will bedescribed.

First, elements configuring the circuit of power transmission device 110are mounted on substrate 100. Then, in the state that power transmittingcoil 111 is connected to power transmission device 110, the power sourceof which the output current is displayed and power transmission device110 are connected.

Next, as shown in FIG. 18, body 20 is inserted into support part 84 ofcharging stand 80. Accordingly, power transmitting coil 111 of chargingstand 80 and power receiving unit 61 of body 20 are disposed in a stateof performing a charging operation. A prescribed voltage (for example, 5V) is set to an external power source, and the voltage is applied toconnection part 90 which is an input part of power transmission device110. This disposition corresponds to a state of the transmission mode.

Next, the output of the PWM signal is changed, and is applied to thegates G of first switching element 112A and second switching element112B. In this case, the output of the PWM signal is adjusted such thatthe output current (a charge current) supplied to power receiving unit61 of body 20 measured with a multimeter falls within a predeterminedrange. In this case, the ON time of the PWM signal when the outputcurrent is included in a predetermined range is set as ON time TX. Then,set ON time TX is stored in a storage unit (not shown) of powertransmission controller 115.

That is, the output of the PWM signal is changed for each of first drivecircuit 114A and second drive circuit 114B, and ON time TX is measuredindividually.

Specifically, ON time TX of the PWM signal of first drive circuit 114Ais measured by changing ON time TX. Then, in a specific PWM signal, ONtime TX when the output current is included in a predetermined range isset as first ON time TXA. Similarly, second ON time TXB is set based onON time TX of a PWM signal of second drive circuit 114B. Then, set firstON time TXA and second ON time TXB are stored as a first fixed value ina storage unit of power transmission controller 115. The first fixedvalue is an exemplification of a fixed value in the transmission mode.

The predetermined range is a range from a lower limit to an upper limitof a target output current (a charge current).

By the above method, ON time TX in the transmission mode is set.

Hereinafter, a method of setting ON time TY in the standby mode will bedescribed.

First, body 20 shown in FIG. 18 is removed from charging stand 80. Powertransmitting coil 111 of charging stand 80 and magnetism collecting coil71 of body 20 are disposed such that a coupling coefficient becomessufficiently sparse (for example, “0”). By this arrangement, a state ofthe standby mode is obtained.

Next, in the standby mode state, because body 20 is not present unlikethe above transmission mode, the output pf the PWM signal is adjustedwhile monitoring the output current of the power source. Then, the ONtime of the PWM signal when the output current is included in apredetermined range is set as ON time TY. Then, set ON time TY is storedin the storage unit, not shown, of power transmission controller 115.The predetermined range is a range of an output current value which isset such that power consumption sufficiently satisfies regulations.

That is, the output of the PWM signal is changed for each of first drivecircuit 114A and second drive circuit 114B, and ON time TY is measuredindividually.

Specifically, ON time TY of the PWM signal of first drive circuit 114Ais measured by changing ON time TY. Then, in a specific PWM signal, ONtime TY when the output current is included in a predetermined range isset as first ON time TYA. Similarly, second ON time TYB is set based onON time TY of a PWM signal of second drive circuit 114B. Then, set firstON time TYA and second ON time TYB are stored as second fixed values inthe storage unit (not shown) of power transmission controller 115. Thesecond fixed value is an exemplification of a fixed value in the standbymode.

By the above method, ON time TY in the standby mode is set.

Examples of first ON times TXA, TYA and second ON times TXB, TYB offirst switching element 112A and second switching element 112B are shownin FIG. 25 to FIG. 29. FIG. 25 to FIG. 29 each show an example of thecase where drive frequency fD is 143 kHz and one cycle T is 7 μs.

Here, (a) and (b) in FIG. 25 show an example of a PWM signal when secondON time TXB is set smaller than first ON time TXA, in the transmissionmode. In this case, first ON time TXA is set to 1 μs, and second ON timeTXB is set to 0.75 μs. Accordingly, as shown in (c) in FIG. 25, thepower-transmitting coil current flowing through power transmitting coil111 of power transmission device 110 becomes in a sinusoidal waveform,for example.

Further, (a) and (b) in FIG. 26 show an example of setting of first ONtime TXA and second ON time TXB in power transmission device 110 whenimpedance Z shown in (a) in FIG. 24 is second impedance ZB, in thetransmission mode. In the case of second impedance ZB, first ON time TXAis set to 1 μs, and second ON time TXB is set to 1 μs.

Further, (a) and (b) in FIG. 27 show an example of setting of first ONtime TXA and second ON time TXB in power transmission device 110 whenimpedance Z shown in (a) in FIG. 24 is first impedance ZA, in thetransmission mode. In the case of first impedance ZA, first ON time TXAis set to 0.75 μs, and second ON time TXB is set to 0.75 μs.

As shown in FIG. 26 and FIG. 27, first ON time TXA and second ON timeTXB of power transmission device 110 showing second impedance ZB are setin larger values than first ON time TXA and second ON time TXB of powertransmission device 110 showing first impedance ZA.

Further, (a) and (b) in FIG. 28 show an example of setting of first ONtime TYA and second ON time TYB in power transmission device 110 whenimpedance Z shown in (a) in FIG. 24 is second impedance ZB, in thestandby mode. In the standby mode, in the case of second impedance ZB,first ON time TYA is set to 0.375 μs, and second ON time TYB is set to0.125 μs. First ON time TXA and second ON time TXB shown in FIG. 26 areset in larger values than first ON time TYA and second ON time TYB shownin FIG. 28.

Further, (a) and (b) in FIG. 29 show an example of setting of first ONtime TYA and second ON time TYB in power transmission device 110 whenimpedance Z shown in (a) in FIG. 24 is first impedance ZA, in thestandby mode. In the standby mode, in the case of first impedance ZA,first ON time TYA is set to 0.125 μs, and second ON time TYB is set to0.125 μs. First ON time TXA and second ON time TXB shown in FIG. 27 areset in larger values than first ON time TYA and second ON time TYB shownin FIG. 29.

That is, from FIG. 26 and FIG. 28, and FIG. 27 and FIG. 29, whenimpedance Z is the same, ON time TX in the transmission mode is set in alarger value than ON time TY in the standby mode.

EXAMPLE

Hereinafter, an example of noncontact power supply device 1 according tothe present exemplary embodiment will be described with reference toFIG. 20 and FIG. 30.

First, design values of components configuring power transmitting coil111 and power receiving unit 61 used in the example will be described.

Power transmitting coil 111 was formed of ten turns of a bundle of 140wires, each wire having a 0.06 mm diameter. Further, power transmittingcoil 111 was formed to have an axial length of 15 mm and an ellipticalshape having a long side of 40 mm and a short side of 30 mm.Accordingly, power transmitting coil 111 was designed such thatinductance L has a design value of 4 μH.

Magnetic core 63 of power receiving unit 61 was formed in a shape of anaxial length of 9 mm and an outer diameter of 12 mm. In this case, anouter diameter of magnetic core 63 was configured to be substantiallyequal (including equal) to the outer diameter of power receiving unit61.

Further, magnetism collecting coil 71 of power receiving unit 61 wasformed of 16 turns of a bundle of 70 wires, each wire having a 0.06 mmdiameter. Magnetism collecting coil 71 was formed in a shape of an axiallength of 6 mm. Accordingly, magnetism collecting coil 71 was designedsuch that inductance L has a design value of 14 μH.

Power receiving coil 62 of power receiving unit 61 was formed of sixturns of a wire of a 0.4 mm diameter. Power receiving coil 62 was formedin a shape of an axial length of 6 mm. Accordingly, power receiving coil62 was designed such that inductance L has a design value of 2 μH.

Next, designed power transmitting coil 111 and power receiving unit 61were disposed as shown in FIG. 20. The output current and the couplingcoefficient were measured while changing distance LC. A result is shownin FIG. 30. Distance LC is an axial distance between center TCC of powertransmitting coil 111 and center RCC of magnetism collecting coil 71 ofpower receiving unit 61 that have been described above.

FIG. 30 shows an experimental result of the output current and thecoupling coefficient obtained for distance LC, in noncontact powersupply device 1 designed as described in the above exemplary embodiment.

As shown in FIG. 30, noncontact power supply device 1 according to theexample has a largest coupling coefficient and a minimum output current,when distance LC is “0”.

On the other hand, as the absolute value of distance LC increases, theoutput current flowing through power transmitting coil 111 increases. Inthis case, the output current becomes maximum in distance LC (forexample, about 10 mm) when the coupling coefficient is near 0.2 andlarger than 0.2. The output current decreases as the absolute value ofdistance LC becomes larger in distance LC when the coupling coefficientis near 0.2 and smaller than 0.2.

That is, it can be understood that, in the case of noncontact powersupply device 1 according to the example, the output current when theabsolute value of distance LC is 4.5 mm increases by about 20% (1.2×I1)more than the output current (for example, I1) when distance LC is 0 mm.

Based on a measurement result in FIG. 30, operation and advantageouseffects of noncontact power supply device 1 will be described below withreference to FIG. 18.

First, as shown in FIG. 18, magnetism collecting coil 71 is disposednear a bottom part of body 20. When body 20 of electric toothbrush 10 issupported by charging stand 80, center TCC of power transmitting coil111 in the axial direction and center RCC of magnetism collecting coil71 in the axial direction are disposed in a shifted manner.

When center TCC of power transmitting coil 111 and center RCC ofmagnetism collecting coil 71 are shifted, the coupling coefficient ofpower transmitting coil 111 and magnetism collecting coil 71 becomessmall, as shown in FIG. 30.

On the other hand, power transmitting coil 111 has an air-core, andmagnetism collecting coil 71 is wound around magnetic core 63. In thiscase, in the axial direction of power transmitting coil 111, as centerRCC of magnetism collecting coil 71 is shifted from center TCC of powertransmitting coil 111, inductance L of power transmitting coil 111decreases. Therefore, from Equation (1), power-transmission resonancefrequency f1 of the power-transmission resonant circuit increases.According to the present exemplary embodiment, power-transmissionresonance frequency f1 is designed to become smaller than drivefrequency fD of first switching element 112A and second switchingelement 112B.

That is, as center RCC of magnetism collecting coil 71 is shifted fromcenter TCC of power transmitting coil 111, power-transmission resonancefrequency f1 approaches drive frequency fD. When power-transmissionresonance frequency f1 and drive frequency fD are closer to each other,the input current increases as shown in (b) in FIG. 24. In this case, asshown in FIG. 30, when the absolute value of distance LC becomes larger(up to about 4.5 mm), the coupling coefficient of power transmittingcoil 111 and magnetism collecting coil 71 becomes smaller, but the inputcurrent increases. As a result, the output current of power receptiondevice 60 can be increased.

Further, magnetic core 63 according to the example is in a bobbin shape.Therefore, the alternating magnetic flux output from power transmittingcoil 111 is easily collected by magnetic core 63. That is, a magneticflux passing through the core of the bobbin shape is bent through acollar portion of magnetic core 63. Therefore, the flux is easilyreturned to power transmitting coil 111. Accordingly, leakage of amagnetic flux is prevented, and a coupling degree of couplingcoefficient of power transmitting coil 111 and magnetism collecting coil71 increases. As a result, a decrease in power transmission efficiencycan be prevented.

As described above, in noncontact power supply device 1 according to thepresent exemplary embodiment, center TCC of power transmitting coil 111and center RCC of magnetism collecting coil 71 are disposed in a shiftedmanner. Accordingly, the above operation and advantageous effects areobtained.

Operation and advantageous effects in the configuration of powerreceiving unit 61 of power reception device 60 will be described belowwith reference to FIG. 31 and FIG. 32, while comparing the operation andadvantageous.

In power receiving unit 61 according to the present exemplaryembodiment, first, magnetism collecting coil 71 is wound aroundbobbin-shaped magnetic core 63, as shown in FIG. 31. Then, by windingpower receiving coil 62 around an outer periphery of magnetismcollecting coil 71, with an insulation tape interposed between thecoils, power receiving unit 61 is configured, for example.

In this case, even when a number of turns of power receiving coil 62 isset smaller than a number of turns of magnetism collecting coil 71, aninfluence to power transmission efficiency is small.

On the other hand, from the viewpoint of transmission efficiency,magnetism collecting coil 71, it is preferable that a Q value that is acharacteristic value of the coil is large. A Q value is expressed by“ωL/r” (r represents a resistance value). Therefore, it is preferable tomake the Q value large by making inductance L large by increasing thenumber of turns of magnetism collecting coil 71.

Therefore, according to the present exemplary embodiment, first,magnetism collecting coil 71 is wound around magnetic core 63 byoverlapping of an even number time, for example, by double. Then, powerreceiving coil 62 is wound by one-fold around the outer periphery ofmagnetism collecting coil 71 which is wound around magnetic core 63.Accordingly, power receiving unit 61 is configured. In this case,because power receiving coil 62 is wound by one-fold around the outerperiphery of magnetism collecting coil 71, winding start part 62A andwinding end part 62B are exposed to an outside of power receiving unit61. Therefore, power receiving coil 62 can be easily connected to eachexternal element.

Further, because magnetism collecting coil 71 is wound by overlapping ofan even number time, winding start part 71A and winding end part 71B canbe disposed on the same side in the axial direction. Therefore, windingstart part 71A and winding end part 71B of magnetism collecting coil 71can be easily pulled outside of power receiving unit 61. Accordingly,winding start part 71A and winding end part 71B of magnetism collectingcoil 71 are easily connected to each external element.

Next, a configuration of magnetism collecting coil 71 and powerreceiving coil 62 of power receiving unit 161 shown as a comparativeexample will be described with reference to FIG. 32.

For power receiving unit 161 shown in FIG. 32, first, power receivingcoil 62 is wound around bobbin-shaped magnetic core 63 by one fold.Then, by winding magnetism collecting coil 71 around the outer peripheryof power receiving coil 62 by overlapping of an even number time, powerreceiving unit 161 is configured. In this case, winding start part 62Aand winding end part 62B of power receiving coil 62 are disposed onopposite sides in the axial direction. Therefore, region RA for pullingout winding end part 62B of power receiving coil 62 needs to be formedon winding end part 62B side. Accordingly, in the case of magnetic core63 of the same shape as that in FIG. 31, a region in which magnetismcollecting coil 71 can be wound becomes small. As a result, the numberof turns of magnetism collecting coil 71 becomes small. Further, becausepower receiving coil 62 is not wound by multiple turns, the outerdiameter can be made small.

That is, for power receiving unit 61 shown in FIG. 31, magnetismcollecting coil 71 is wound around bobbin-shaped magnetic core 63, andpower receiving coil 62 is wound around the outer periphery of magnetismcollecting coil 71. Therefore, it is not necessary to form region RA,unlike power receiving unit 161 of the comparative example shown in FIG.32. Accordingly, reduction in the number of turns of magnetismcollecting coil 71 can be prevented. As a result, a Q value of magnetismcollecting coil 71 can be increased.

Effects of noncontact power supply device 1 configured as describedabove will be described in detail by listing.

(1) Power transmission controller 115 grasps ON time TX by measuring inadvance ON time TX such that the output current (a charge current) ofthe power receiving unit is included within a predetermined range, inthe transmission mode. Grasped ON time TX is stored as the first fixedvalue in the storage unit of power transmission controller 115. In thiscase, the predetermined range is a range from a permissible upper limitto lower limit of a charge current. Then, by using a first fixed valueset in advance, in the transmission mode, power transmission device 110is driven. Accordingly, it is not necessary to perform feedback based onthe output current. As a result, more proper power transmissionefficiency is obtained.

Further, it is not necessary to mount a circuit for feedback. Therefore,a configuration of noncontact power supply device 1 can be simplified.

Further, it is not necessary to change power-transmission resonancefrequency f1 and magnetism-collection resonance frequency f2corresponding to the power-reception resonance frequency, by using avariable capacitor. Accordingly, by avoiding use of a large-typecapacitor, increase in size of noncontact power supply device 1 can beprevented. Further, it is not necessary to include a plurality ofcapacitors and change power-transmission resonance frequency f1 andmagnetism-collection resonance frequency f2 by changing to a propercapacitor. Accordingly, increase in size of power transmission device110 can be prevented. That is, power transmission controller 115controls to reduce the variation in the power-transmitting coil currentflowing through power transmitting coil 111, by using onepower-transmission resonant capacitor 116. Therefore, as compared withthe case of using a variable capacitor or a plurality of capacitors,increase in size of noncontact power supply device 1 can be prevented.

(2) Usually, when there exists an error such as a manufacturingvariation in the values of a plurality of switching elements, ON timesTX necessary to include an output current (a charge current) within apredetermined range are mutually different. Therefore, powertransmission controller 115 according to the present exemplaryembodiment sets ON times TX of first switching element 112A and secondswitching element 112B, by individually measuring in advance ON timesTX. Therefore, more proper power transmission efficiency is obtained.Further, by individually setting ON times TX, the power-transmittingcoil current can be finely adjusted. Accordingly, even in theconfiguration of power transmission controller 115 with low resolutionin the PWM signal, the power-transmitting coil current can be properlyadjusted.

(3) Power transmission controller 115 grasps ON time TY by measuring inadvance ON time TY such that the output current is included within apredetermined range, in the standby mode. Grasped ON time TY is storedas the second fixed value in the storage unit of power transmissioncontroller 115. In this case, the predetermined range is a range of theoutput current prescribed for reducing the power consumption. Then, byusing a second fixed value set in advance, in the standby mode, powertransmission device 110 is driven. Accordingly, it is not necessary toperform feedback control based on the output current. As a result, powerconsumption is properly reduced.

(4) Because magnetism collecting device 70 is not electrically connectedto rechargeable battery 41, a Q value can be easily set larger than thatof power receiving coil 62. Then, a magnetic flux output from powertransmitting coil 111 is interlinked with magnetism collecting coil 71,and a magnetic flux output from magnetism collecting coil 71 isinterlinked with power receiving coil 62. Accordingly, powertransmission efficiency can be more increased than when magnetismcollecting device 70 does not exist.

(5) Usually, a noncontact power supply device including a magnetismcollecting circuit can further increase power transmission efficiency,when drive frequency fD and power-transmission resonance frequency f1 ofeach switching element are substantially coincided with power-receptionresonance frequency f2 of a magnetism collecting circuit. However, inorder to make frequencies fD, f1, f2 coincide with each other, highprecision adjustment becomes necessary. Therefore, there is a concernabout reduction in productivity of a noncontact power supply device.Therefore, in noncontact power supply device 1 according to the presentexemplary embodiment, frequencies fD, f1, f2 are set to mutuallydifferent values. Therefore, it is not necessary to make frequencies fD,f1, f2 coincide with each other. Accordingly, even when there arevariations such as manufacturing errors (tolerance) in the components,high precision adjustment becomes unnecessary. As a result, it ispossible to increase productivity of noncontact power supply device 1.

Further, power-transmission resonance frequency f1 is set smaller thandrive frequency fD. Therefore, as compared with a case wherepower-transmission resonance frequency f1 is higher than drive frequencyfD, operations of first switching element 112A and second switchingelement 112B are stabilized. That is, when power-transmission resonancefrequency f1 is set smaller than drive frequency fD, inductive resonanceoccurs in a resonant circuit. Therefore, noise (ringing of a current)does not easily occur, and an operation becomes stable. Accordingly,power transmission efficiency does not easily decrease.

Further, when power-reception resonance frequency f2 is larger thandrive frequency fD, stable output can be obtained against a variation ina load, as compared with a case where power-reception resonancefrequency f2 is smaller than drive frequency fD. The inventors of thepresent invention have confirmed this effect by tests.

By the above, noncontact power supply device 1 with high powertransmission efficiency and with excellent productivity can be realized.

(6) Usually, when a difference between drive frequency fD andpower-transmission resonance frequency f1 is smaller, power transmissionefficiency can be increased. In noncontact power supply device 1according to the present exemplary embodiment, a lower limit (85%) ofpower-transmission resonance frequency f1 is prescribed. Therefore, highpower transmission efficiency can be secured.

(7) In noncontact power supply device 1 according to the presentexemplary embodiment, even when a coupling coefficient is included inany one of a first range and a second range which are mutuallydifferent, or even when the body is not disposed in the powertransmission device, a large and small relationship between drivefrequency fD of first switching element 112A and second switchingelement 112B and power-transmission resonance frequency f1 ismaintained. Therefore, the influence of an arrangement position ofmagnetism collecting device 70 in power transmission device 110 to aninfluence of switching can be prevented. Accordingly, the possibility ofreduction in power transmission efficiency can be reduced.

(8) In a state that center TCC of power transmitting coil 111 in theaxial direction is shifted from center RCC of magnetism collecting coil71 in the axial direction, rechargeable battery 41 as a load is charged.Therefore, as described with reference to FIG. 30, the output currentcan be made large as compared with the case where centers of powertransmitting coil 111 and magnetism collecting coil 71 in their axialdirection coincide with each other. Accordingly, noncontact power supplydevice 1 that can transmit larger power can be realized.

(9) Noncontact power supply device 1 according to the present exemplaryembodiment includes power receiving coil 62 and magnetism collectingcoil 71 that are wound around bobbin-shaped magnetic core 63 thatincludes a magnetic material. Therefore, a magnetic flux that interlinkswith power transmitting coil 111 and magnetism collecting coil 71 doesnot easily leak. Accordingly, power transmission efficiency can be moreincreased.

Further, magnetism collecting coil 71 and power receiving coil 62 arewound around one magnetic core 63. Therefore, a configuration ofnoncontact power supply device 1 can be simplified.

Modification

Description concerning the present exemplary embodiment illustrates apossible exemplary embodiment of the noncontact power supply deviceaccording to the present invention. Therefore, it is not intended tolimit the possible exemplary embodiment of the noncontact power supplydevice. In other words, the noncontact power supply device according tothe present invention can adopt, in addition to the present exemplaryembodiment, for example, modification of the exemplary embodiment shownbelow, and a mode of combination of at least two modifications that arenot mutually inconsistent.

That is, in the present exemplary embodiment, an example of aconfiguration in which ON times TX, TY are set by measurement of theoutput current (charge current) has been described. However, the presentexemplary embodiment is not limited to this example. For example, ONtimes TX, TY may be set based on the input current. In this case, the ONtimes of the PWM signal when the input current is included in apredetermined range are set as ON times TX, TY. Then, set ON times TX,TY are stored in the storage unit of power transmission controller 115.Further, ON times TX, TY may be set based on a resonance voltage V. Inthis case, the ON times of the PWM signal when resonance voltage V isincluded in a predetermined range are set as ON times TX, TY. Then, setON times TX, TY are stored in the storage unit of power transmissioncontroller 115. Further, ON times TX, TY may be set based on thepower-transmitting coil current of power transmitting coil 111. In thiscase, the ON times of the PWM signal when the power-transmitting coilcurrent is included in a predetermined range are set as ON times TX, TY.Then, set ON times TX, TY are stored in the storage unit of powertransmission controller 115. Set ON times TX, TY correspond to first ONtime TXA and second ON time TXB in the transmission mode. Set ON timesTX, TY correspond to first ON time TYA and second ON time TYB in thestandby mode.

Further, in the present exemplary embodiment, power transmission device110 has been described based on an example of configuring powertransmission device 110 with a half-bridge circuit shown in FIG. 21.However, the present exemplary embodiment is not limited to thisexample. For example, power transmission device 110 may be configured bya full-bridge circuit shown in FIG. 33. In this case, power transmissiondevice 210 includes first switching element 212A, second switchingelement 212B, third switching element 212C, fourth switching element212D, smoothing capacitor 213, first drive circuit 214A, second drivecircuit 214B, third drive circuit 214C, and fourth drive circuit 214D.

Then, in power transmission device 210 shown in FIG. 33, ON time TZ of aPWM signal to be input to gate G of each switching element is set, asshown in (a), (b), (c), and (d) of FIG. 34. In this case, as shown in(a) and (d) of FIG. 34, ON time TZA of first switching element 212A andON time TZD of fourth switching element 212D are set to become equal.Similarly, as shown in (b) and (c) of FIG. 34, ON time TZB of secondswitching element 212B and ON time TZC of third switching element 212Care set to become equal. Accordingly, as shown in (e) of FIG. 34, apower-transmitting coil current flowing through power transmitting coil111 of power transmission device 210 becomes in a sinusoidal waveform,for example. In the case of a full-bridge, a power source voltagebecomes double, so that output can be increased.

Further, in the present exemplary embodiment, power reception device 60has been described by taking an example that alternating power of powerreceiving coil 62 is half-wave rectified. However, the alternating powermay be full-wave rectified. Accordingly, power loss can be reduced.

Further, in the present exemplary embodiment, power receiving coil 62has been described by taking an example that power receiving coil 62 isdisposed on an outer periphery of magnetism collecting coil 71. However,when there is margin in the space, power receiving coil 62 may bedisposed on an inner periphery.

Further, in the present exemplary embodiment, magnetism collectingdevice 70 has been described by taking an example of a configurationthat magnetism collecting device 70 is included in electric toothbrush10 which is a small electric device. However, magnetism collectingdevice 70 may be configured to be included in charging stand 80.Accordingly, the body can be made compact.

Further, in the present exemplary embodiment, magnetism collectingdevice 70 may be omitted. In this case, in place of magnetism-collectingresonant capacitor 72, a power-reception resonant capacitor is connectedto power receiving coil 62. Then, a power-reception resonant circuit isconfigured by power receiving coil 62 and a power-reception resonantcapacitor. In this case, a resonance frequency of a power-receptionresonant circuit including power receiving coil 62 and a power-receptionresonant capacitor corresponds to power-reception resonance frequencyf2. Accordingly, a number of components can be reduced.

Further, in the present exemplary embodiment, magnetic core 63 may beformed in a rod shape. Further, by omitting magnetic core 63, powerreceiving coil 62 and magnetism collecting coil 71 may be configured byfixing by heat-welding. Accordingly, the body can be made compact.

The noncontact power supply device according to the present exemplaryembodiment may be applied to a noncontact power supply device thatincludes an oral cleaning machine for cleaning an oral cavity byejecting water, or a stain cleaner for removing stains by polishingteeth, a shaver, or a hair remover. Accordingly, because an electriccontact becomes unnecessary, the noncontact power supply device can besafely used around water.

(An Example of a Possible Exemplary Embodiment of a Control Device for aNoncontact Power Supply Device)

(1) A control device for a noncontact power supply device according toone exemplary embodiment of the present invention is a powertransmission device for a noncontact power supply device, the powertransmission device including: a resonant circuit (a power-transmissionresonant circuit) that outputs an alternating magnetic flux by powersupplied from a power source circuit; a plurality of switching elementsthat are switched such that the alternating magnetic flux is generatedin the resonant circuit; and a power transmission controller thatcontrols the plurality of switching elements to transmit power to apower receiving coil of a power reception device by the alternatingmagnetic flux. The power transmission controller includes a transmissionmode for supplying alternating power to the resonant circuit byrepeating the ON and OFF of the plurality of switching elements. Then,ON time in one cycle of operation of each of the switching elements inthe transmission mode may be set as a first fixed value.

According to the present configuration, ON time is grasped in advancesuch that the output current (a charge current) of the power receivingunit is included within a predetermined range, in the transmission mode.Then, the grasped ON time is stored as a first fixed value in a storageunit of the power transmission device. In this case, the predeterminedrange is a range of the output current prescribed to include the powertransmission efficiency in a preferable range. Then, a first fixed valueset in advance is used in the transmission mode. Accordingly, it is notnecessary to perform feedback control based on the output current. As aresult, more proper power transmission efficiency is obtained. Further,it is not necessary to mount a circuit for feedback control. Therefore,a configuration of a noncontact power supply device can be moresimplified.

(2) According to one example of the control device for a noncontactpower supply device, the ON time of each of the plurality of switchingelements may be set individually.

In general, when there exists a manufacturing variation in capacitorsand coils which are components, ON time necessary to include an inputcurrent or an output current within a predetermined range are mutuallydifferent. According to the above configuration, the ON time of each ofthe plurality of switching elements are set individually. Therefore,more proper power transmission efficiency is obtained.

(3) According to one example of the control device for a noncontactpower supply device, the power transmission controller includes astandby mode for supplying, to the resonant circuit, the alternatingpower smaller than the alternating power in the transmission mode byrepeating the ON and OFF of a plurality of switching elements. Then, ONtime in one cycle of operation of each of the switching elements in thestandby mode may be set as a second fixed value.

According to this configuration, the ON time is grasped in advance suchthat the input current or the output current in the standby mode isincluded in a predetermined range, and the second fixed value as a fixedvalue indicating the ON time is stored in the storage unit of thecontrol device. The predetermined range is a range of the input currentor output current prescribed to reduce the power consumption. Then, thesecond fixed value set in advance is used in the standby mode, so thatpower consumption can be properly reduced even when feedback based onthe input current or the output current is not performed.

(4) According to one example of the control device for a noncontactpower supply device, the ON time of the first fixed value may be setlarger than the ON time of the second fixed value. Accordingly, powerconsumption in the standby mode can be reduced.

(5) According to one example of the control device for a noncontactpower supply device, the ON time may be determined such that the inputcurrent supplied to the resonant circuit or the output current outputfrom the resonant circuit is included in a predetermined range.Accordingly, a control device for a versatile noncontact power supplydevice is obtained.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a power transmission device forvarious kinds of noncontact power supply devices that are used in homes,medical organizations, or equivalent environments.

1. A power transmission device for a noncontact power supply device, thepower transmission device comprising: a resonant circuit that outputs analternating magnetic flux by power supplied from a power source circuit;a plurality of switching elements that are switched such that thealternating magnetic flux is generated in the resonant circuit; and apower transmission controller that controls the plurality of switchingelements to transmit power to a power receiving coil of a powerreception device by the alternating magnetic flux, wherein the powertransmission controller includes a transmission mode for supplyingalternating power to the resonant circuit by repeating ON and OFF of theplurality of switching elements, and ON time in one cycle of operationof each of the switching elements in the transmission mode is set as afirst fixed value.
 2. The power transmission device for a noncontactpower supply device according to claim 1, wherein the ON time of each ofthe plurality of switching elements are set individually.
 3. The powertransmission device for a noncontact power supply device according toclaim 1, wherein the power transmission controller includes a standbymode for supplying, to the resonant circuit, the alternating powersmaller than the alternating power in the transmission mode by repeatingthe ON and OFF of the plurality of switching elements, and ON time inone cycle of operation of each of the switching elements in the standbymode is set as a second fixed value.
 4. The power transmission devicefor a noncontact power supply device according to claim 1, wherein theON time of the first fixed value is larger than the ON time of thesecond fixed value.
 5. The power transmission device for a noncontactpower supply device according to claim 1, wherein the ON time isdetermined such that an input current supplied to the resonant circuitor an output current supplied from a power receiving unit to a load isincluded in a predetermined range.